Cryptocurrencies designed to maintain a stable value, usually pegged 1:1 to USD (USDT, USDC, DAI).
Example
You sell Bitcoin in a downtrend and park the proceeds in USDT — a stablecoin pegged 1:1 to the US dollar. That keeps you in crypto without exposure to volatility, and you can re-enter quickly at any time. Stablecoins are the bridge between crypto and fiat. Backing matters: USDC and USDT are covered by reserves, whereas algorithmic stablecoins (like UST once was) can collapse.